1. Field of the Invention
The present general inventive concept relates to a pickup roller and an image forming apparatus having the same.
2. Description of the Related Art
An electrophotographic image forming apparatus develops an image by forming an electrostatic latent image by scanning a light beam over a photosensitive drum by using a light scanner, forming a developed image by developing the electrostatic latent image by using a developing agent (e.g. a toner), transferring the developed image onto a printing medium, and fixing the transferred image to the printing medium.
Such an electrophotographic image forming apparatus includes a pickup roller to pick up a printing medium from a plurality of printing media stacked in a cassette and to transport the picked-up printing medium into the electrophotographic image forming apparatus. It is necessary for such a pickup roller to pick up a printing medium at a constant rate regardless of characteristics of the printing medium and without slipping or damaging the printing medium.
However, as a pickup roller has been used for a certain period of time, it becomes difficult to pick up a printing medium due to abrasion or pollution of the surface of the pickup roller. The problem is significant for a pickup roller employing soft rubber.
When relatively hard rubber is used to resolve the problem, the durability against abrasion of the surface of a pickup roller may be resolved. However, in this case, a printing medium may not be properly transported due to characteristics thereof (e.g. basis weight, thickness, surface characteristics), because it is difficult to achieve sufficient friction between the hard rubber and the printing medium.
Furthermore, when a pressure applied to a printing medium is increased to achieve higher friction between a pickup roller employing hard rubber and the printing medium, the printing medium may be damaged, and the durability of the pickup roller may also deteriorate due to pollution or destruction of the surface of the pickup roller. Therefore, a durable pickup roller, which applies a relatively small amount of pressure to a printing medium and maintains sufficient friction between the pickup roller and the printing medium, is required.